Material and method for making stencil masters



Nov. 14, 1967 c. H. STEIN ETAL MATERIAL AND METHOD FOR MAKING STENCIL MASTERS Filed Dec. 13, 1963 F'KS. 3

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INVENTORS CHARLES H. STEIN BY WILLIAM R. KRAUSE ATTORNEY United States Patent 3,352,728 MATERIAL AND METHOD FOR MAKING STENCIL MASTERS Charles H. Stein, Westwood, and William R. Krause,

Secaucus, N.J., assignors to Keuifei & Esser Co., Hoboken, N.J., a corporation of New Jersey Filed Dec. 13, 1963, Ser. No. 330,455 6 Claims. (Cl. 1563) The present application is a continuation-in-part of application Ser. No. 817,852, filed June 3, 1959 now abandoned, and the invention relates to processes and materials for making master templates for cartography circuit, cards, and the like where accurate duplications are essential for accurate registry in maps and to obtain constant electrical characteristics in duplicate circuit cards including constant resistance of conductors and constant capacitance between adjacent conductors in each completed circuit card.

An object of the present invention is to provide means and method to obtain accurate reproductions in cartography and in circuit cards with a minimum of variation and a minimum of skilled personnel.

Another object is to provide methods of producing accurate masters for graphic arts.

A further object is to provide a method of making a finished circuit card involving a master pattern or template from which the circuit card is duplicated.

Other and further objects will be apparent as the description proceeds and upon reference to the accompanying drawings, wherein:

FIGURE 1 is a fragment of a modified film including a transparent base, a peelable coating, and a top scribe coating thereon through which scribed lines made by scribing tools outline a section of a circuit or the like.

FIGURE 2 is a fragmentary section taken substantially on line 2-2 of FIGURE 1.

FIGURE 3 is a section taken on line 33 of FIGURE 4 showing etching of the second coating.

FIGURE 4 shows peeling of the second coating and the top scribe coating between the selected scribed and etched lines to provide a large window area in the coating.

FIGURE 5 is a section taken substantially on the line 55 of FIGURE 4 showing the open window area formed by the removal of the strip of coating between the etched lines.

FIGURE 6 shows a peelable layer on one surface of a transparent base and a pencil-take coating on the other surface with a scribe coat on the peelable layer.

Material according to the present invention may be readily prepared as follows. The base film 4 is provided with a peelable or strippable coating layer 6 of visually transparent material such as polyvinyl alcohol resin on its front surface.

The peelable or strippable layer or coat 6 is made as follows:

Lbs. Polyvinyl alcohol 10 Water 90 The polyvinyl alcohol resin is made from polyvinyl acetate which is hydrolyzed in a range from 85% to 100%. A medium high viscosity grade with the molecular weight in the range of 120,000 to 220,000 is used. Such polyvinyl resin is applied in a water solution thereof by any suitable means and the water is evaporated leaving the polyvinyl alcohol resin of a thickness of 0.2 mil while the base film 4 is normally 7.5 mil thick. To make the polyvinyl alcohol layer peel coat opaque to actinic light a suitable pigment or dye is included in the water solution thereof. Suitable pigments are titanium dioxide, copper phthalocyanine, and lead chromate for example which are pres- 3,352,728 Patented Nov. 14, 1967 ent in an amount of 10% based on the weight of the polyvinyl alcohol. Suitable dyes are water soluble dyes such as acid dyes and Rhodamine B Extra CT 45170. A typical amount of dye is 1% based on the weight of polyvinyl alcohol.

On top of the peelable layer 6 a visually transparent actinically opaque scribable coating or layer 7 is provided wherein desired outlines can be scribed through the scribable coating 7 by means of suitable scribing devices.

A suitable composition for the scribe coat 7 is made from:

Lbs. Phthalic anhydride 12.3 Glycerin 7.2 Linoleic acid 23 The above provides the solids in alkyd resin solution which solids are dissolved in 42.5 lbs. of mineral spirits having a boiling point in the order of 200 to 300 de grees F.

The pigments of the scribe coat are made from:

Calcium carbonate lbs 150 Lead chromate lbs 50 Cobalt naphthanate in a 6% solution in mineral spirits oz 2 Mineral spirits lbs The pigments are finely dispersed in the alkyd resin with the particle size of the pigments being in the range of 1 to 25 microns and such scribe coat provides a matte surface on which pencil lines may be drawn if desired. The scribe coating can be etched with ethyl acetate or acetone if etching is desired.

The material thus prepared is utilized in the production of a master transparency in the following manner as depicted in FIGURES 1-5.

A desired outline 9 is scribed through coating 7 to uncover the underlying polyvinyl alcohol peelable layer 6. The peelable layer 6 is then etched away beneath the scribed outline 13 to provide a deep outline 1S penetrating to the surface of the base film 4. Peelable layer 6 is readily etched with water which dissolves the polyvinyl alcohol without effecting the alkyd resin of the scribe layer.

The portions 17 of the composite coating within the outline are then peeled away from the film base 4, thereby providing an open window area 19 in an opaque coating 7 and forming a master stencil.

The master stencil may be used in the usual photo-etch process where it is applied with its scribe coated surface 7 in contact printing directly to the photosensitive surface of a circuit card which includes an insulating base material, copper or other conductive layer and a photosensitive layer and the final circuit is etched out on the circuit card. The exposureof the photosensitive surface of the circuit card through the stencil master to the light of a common source such as a Sylvania Concentrated Arc or LTF light source can also be made by a photographic enlarging or reduction process. The length of exposure will depend on light intensity.

Due to the visual transparency of the peelable and scribable layers, the master material may be positioned over an original drawing or print and the desired outline traced in the scribe layer with a scribing tool. Alternatively, the back surface of the base film 23 (FIG. 6) may 'have a matte surface coating 25 on which a pencil outline may be drawn. A scribe tracing in layer 27 and etching of peel layer 29 prepare the material for the formation of open window areas by peeling away the coating within the outline as previously described. The pencil- .3 take matte surface 25 may be made by applying a lacquer of the following composition to the back surface of the base film 23:

Lbs. Amorphous silica 60 Nitro cellulose 25 Dioctylphthalate Ethyl acetate 150 Toluene 150 The amorphous silica has particles in the range of 1 to microns and the nitro cellulose solution is a low viscosity type such as measured by the falling ball method in one-quarter of a second.

In some instances, the scribable coat may be made visually as well as actinically opaque. Under such circumstances, an original outline may be drawn on the pencil-take surface of the scribe coat and the outline traced with a scribing tool.

It will be apparent that the peelable layer of the present invention is sufficiently flexible and of sufiicient strength with a limited adhesion to a subbing layer or the base so that after the peelable layer is cut or etched to provide window defining groove lines, the peelable coat between the grooved lines can be removed by a stripping or peeling action in the manner above described. The resulting stencil formed is opaque to actinic light in the non-window areas, since at least one of the scribe coat and the peelable layer is made opaque to actinic light.

From the above description, it will be seen that a new method has been provided in which an open window master can be made from a scribed image for use in cartography, electric circuits and the like where great accuracy is required.

It will be obvious to those skilled in the art that various changes may be made in the invention without departing from the spirit and scope thereof and therefore the invention is not limited by that which is illustrated in the drawings and described in the specification, but only as indicated in the accompanying claims.

We claim:

1. Material for making a stencil master for photographic reproduction comprising:

(a) a base sheet transparent to visible and actinic light;

(b) a peel layer on a surface of said base sheet, said peel layer comprising polyvinyl alcohol and suflicient strength with a'limited adhesion to said base sheet whereby said peel layer may be peeled from said base sheet as a continuou film, said peel layer further being soluble in a predetermined solvent; and

(c) a scribe layer on said peel layer, said scribe layer consisting essentially of finely divided pigment uniformly dispersed in a continuous layer of an alkyd resin whereby groove portions of said scribe layer may be readily removed from said peel layer by a scribe, said scribelayer further being insoluble in said predetermined solvent;

at least one of said peel layer and'said scribe layer being opaque to actinic light.

2. Material according to claim 1 wherein said peel and scribe layers are transparent to at least one spectral band of visible light situated outside the spectral band range of said actinic light.

3. Material according to claim 1 wherein said scribe layer is opaque to actinic light.

4. Material according to claim 1 wherein said peel layer is opaque to actinic light.

5. Material according to claim 4 wherein said peel layer includes a dye opaque to actinic light.

6. The method of making a stencil master for photographic reproduction comprising:

(a) providing material according to claim 1;

(b) scribing an outline in the scribe layer, thereby exposing the peel layer beneath the scribed outline;

(c) applying to the thus-exposed peel layer a solvent for said peel layer, which solvent is a non-solvent for said scribe layer, thereby dissolving the peel layer in a pattern corresponding to the scribed outline and extending said scribed outline to the base sheet; and (d) peeling away from said base sheet areas of said peel layer enclosed within said outline, thereby removing areas of superposed scribe and peel layers and forming a stencil master comprising transparent window areas in an actinically opaque background.

References Cited UNITED STATES PATENTS 1,655,127 1/1928 Beebe 96-36 1,877,310 9/1932 Heidenhain 96-116 2,373,489 4/1945 Marx 96-45 2,383,568 8/1945 Rudnick 117-355 2,484,451 10/1949 Griggs 96-36 2,777,200 1/1957 Wood 33-18 2,810,960 10/1957 Johnson et al. 33-18 2,888,335 5/1959 Atkins et al. 156-12 2,943,936 7/1960 Spechler 96-35 3,052,957 9/1962 Swanson 29-1555 3,061,911 9/1962 Baker 29-555 3,067,034 12/1962 Chapman 96-83 3,080,232 3/1963 Gilbody et al. W 96-35 3,169,063 2/1965 Johnson et al. 96-27 3,171,741 3/1965 Meyer 96-27 OTHER REFERENCES Modern Plastics Encyclopedia, 1951, p. 348. (TP 986.A2 M5 also copy 96-36.)

Military Standardization Handbook, Glossary" of Photographic Terms TM 11-411, TK655OU69C Feb. 3, 1961, p. 3 relied on.

Photo Methods for Industry,. Innovation Speeds GE Printed Circuit Plans, vol. 3, No. 2 (February 1960), TRI. P18 (pp. 54, and 91 relied on).

NORMAN G. TORCHIN, Primary Examiner.

WHITMORE A. WILTZ, ALEXANDER D. RICCI,

Examiners.

C. BOWERS, P. M. COHEN, Assistant Examiners, 

1. MATERIAL FOR MAKING A STENCIL MASTER FOR PHOTOGRAPHIC REPRODUCTION COMPRISING: (A) A BASE SHEET TRANSPARENT TO VISIBLE AND ACTINIC LIGHT; (B) A PEEL LAYER ON A SURFACE OF SAID BASE SHEET, SAID PEEL LAYER COMPRISING POLYVINYL ALCOHOL AND SUFFCIENT STRENGTH WITH A LIMITED ADHESION TO SAID BASE SHEET WHEREBY SAID PEEL LAYER MAY BE PEELED FROM SAID BASE SHEET AS A CONTINUOUS FILM, SAID PEEL LAYER FURTHER BEING SOLUBLE IN A PREDETERMINED SOLVENT; AND (C) A SCRIBE LAYER ON SAID PEEL LAYER, SAID SCRIBE LAYER CONSISTING ESSENTIALLY OF FINELY DIVIDED PIGMENT UNIFORMLY DISPERSED IN A CONTINUOUS LAYER OF AN ALKYD RESIN WHEREBY GROOVE PORTIONS OF SAID SCRIBE LAYER MAY BE READILY REMOVED FROM SAID PEEL LAYER BY A SCRIBE, SAID SCRIBE LAYER FURTHER BEING INSOLUBLE IN SAID PREDETERMINED SOLVENT; AT LEAST ONE OF SAID PEEL LAYER AND SAID SCRIBE LAYER BEING OPAQUE TO ACTINIC LIGHT.
 6. THE METHOD OF MAKING A STENCIL MASTER FOR PHOTOGRAPHIC REPRODUCTION COMPRISING: (A) PROVIDING MATERIAL ACCORDING TO CLAIM 1; (B) SCRIBING AN OUTLINE IN THE SCRIBE LAYER, THEREBY EXPOSING THE PEEL LAYER BENEATH THE SCRIBED OUTLINE; (C) APPLYING TO THE THUS-EXPOSED PEEL LAYER A SOLVENT FOR SAID PEEL LAYER, WHICH SOLVENT IS A NON-SOLVENT FOR SAID SCRIBE LAYER, THEREBY DISSOLVING THE PEEL LAYER IN A PATTERN CORRESPONDING TO THE SCRIBED OUTLINE AND EXTENDING SAID SCRIBED OUTLINE TO THE BASE SHEET; AND (D) PEELING AWAY FROM SAID BASE SHEET AREAS OF SAID PEEL LAYER ENCLOSED WITHIN SAID OUTLINE, THEREBY REMOVING AREAS OF SUPERPOSED SCRIBE AND PEEL LAYERS AND FORMING A STENCIL MASTER COMPRISING TRANSPARENT WINDOW AREAS IN AN ACTINICALLY OPAQUE BACKGROUND. 